1. Field of the Invention
The present invention relates to a keyless entry device that performs predetermined control such as locking and unlocking of doors or the like of a vehicle by performing communication between a vehicle-side device and a portable device.
2. Description of the Related Art
A keyless entry device in which wireless communication is performed between a vehicle-side device provided in a vehicle and a portable device carried by a user, and doors of the vehicle are locked or unlocked based on this communication has been proposed (for example, Japanese Unexamined Patent Application Publication No. 2010-181295). In the keyless entry device, the vehicle-side device includes a plurality of transmission antennas provided in various places in the vehicle, and the portable device calculates a distance from the vehicle-side device based on reception intensity of a signal transmitted from each transmission antenna of the vehicle-side device and performs control of locking and unlocking of the doors of the vehicle according to a result of the calculation.
However, in the keyless entry device of the related art, if a user carries other information devices such as a smartphone, the portable device may receive radio waves generated by the information device as noise, in addition to a signal transmitted from the vehicle-side device, and accuracy of a distance calculated from reception intensity may be degraded. Further, intensity of radio waves generated by the information device such as the smart phone often periodically varies, and it is difficult to exactly recognize the influence of the varying intensity.